Photographic film unit

ABSTRACT

A SELF-DEVELOPING, PHOTOGRAPHIC FILM UNIT INCLUDING A PAIR OF RECTANGULAR SUPPORT SHEETS, ONE OF WHICH IS TRANSPARENT, SECURED IN FACE-TO-FACE RELATION AT THEIR LATERAL MARGINS AND AT ONE END BY BINDING STRIPS. THE MARGINS OF THE TRANSPARENT SUPPORT SHEET EXTEND BEYOND THE EDGES OF THE OTHER SHEET AND THE BINDING STRIPS ARE SECURED TO AND OVERLAP THE LATERAL MARGINS AND ONE END MARGIN OF BOTH SHEETS. A PHOTOSENSITIVE IMAGE-RECORDING LAYER AND AN IMAGE-RECEPTIVE LAYER ARE SANDWICHED BETWEEN THE SHEETS, PREFERABLY WITH THE IMAGE-RECEPTIVE LAYER CLOSEST THE TRANSPARENT SHEET. A CONTAINER OF A LIQUID PROCESSING AGENT ADAPTED TO INITIATE FORMATION OF A VISIBLE TRANSFER IMAGE IN THE IMAGE-RECEPTIVE LAYER WHEN DISTRIBUTED BETWEEN THE SHEETS FOR PERMEATION INTO THE PHOTOSENSITIVE LAYER FOLLOWING EXPOSURE THEREOF, IS COUPLED TO THE SHEETS AT THE OTHER END EDGE OF THE SMALLER SHEET SO AS TO DISPENSE ITS LIQUID CONTENTS BETWEEN THE SHEETS IN RESPONSE TO THE APPLICATION OF COMPRESSIVE PRESSURE. A MASKING LAYER INCLUDING A REFLECTIVE PIGMENT CARRIER IN A BINDER IS COATED OR THE SIDE OF THE TRANSPARENT SHEET FACING THE SMALLER SHEET AND EXTENDS TO THE EGES OF THE TRANSPARENT SHEET. THE MASKING LAYER IS FORMED WITH A RECTANGULAR OPENING SMALLER THAN THE SMALLER SHEET AND IS LOCATED BETWEEN THE PHOTOSENSITIVE AND IMAGE-RECORDING LAYERS OR BETWEEN THE LATTER AND THE TRANSPARENT SHEET TO PROVIDE A REFLECTIVE BORDER SURROUNDING THE VISIBLE IMAGE FORMED IN THE IMAGE-RECORDING LAYER. THE SHEETS AND LAYERS OF THE FILM UNIT MAY BE LAMINATED TO ONE ANOTHER TO FORM AN INTEGRAL UNIT OR THE TWO SUPPORT SHEET AND THE LAYERS CARRIED THEREON MAY BE SECURED TO ONE ANOTHER ONLY AT THEIR MARGINS.

p 26, 1972 R. B. DOWNEY 3,694,206

PHOTOGRAPHIC FILM UNIT Filed Dec, 29, 1970 50 M i f f" FIG. 2

, INVENTOR.

ROGERS B. DOWN EY United States Patent 3,694,206 PHOTOGRAPHIC FILM UNITRogers B. Downey, Lexington, Mass., assignor to Polaroid Corporation,Cambridge, Mass. Filed Dec. 29, 1970, Ser. No. 102,447 Int. Cl. G03c5/54 U.S. Cl. 96-29 R 27 Claims ABSTRACT OF THE DISCLOSURE Aself-developing, photographic film unit including a pair of rectangularsupport sheets, one of which is transparent, secured in face-to-facerelation at their lateral margins and at one end by binding strips. Themargins of the transparent support sheet extend beyond the edges of theother sheet and the binding strips are secured to and overlap thelateral margins and one end margin of both sheets. A photosensitiveimage-recording layer and an image-receptive layer are sandwichedbetween the sheets, preferably with the image-receptive layer closestthe transparent sheet. A container of a liquid processing agent adaptedto initiate formation of a visible transfer image in the image-receptivelayer when distributed between the sheets for permeation into thephotosensitive layer following exposure thereof, is coupled to thesheets at the other end edge of the smaller sheet so as to dispense itsliquid contents between the sheets in response to the application ofcompressive pressure. A masking layer including a reflective pigmentcarried in a binder is coated or the side of the transparent sheetfacing the smaller sheet and extends to the edges of the transparentsheet. The masking layer is formed with a rectangular opening smallerthan the smaller sheet and is located between the photosensitive andimage-recording layers or between the latter and the transparent sheetto provide a reflective border surrounding the visible image formed inthe image-recording layer. The sheets and layers of the film unit may belaminated to one another to form an integral unit or the two supportsheets and the layers carried thereon may be secured to one another onlyat their margins.

BACKGROUND OF THE INVENTION A number of U.S. patents disclose and/orclaim the structure of self-developing film unit particularly adapted tothe production of images in full color by processes involving diffusiontransfer. Such patents include, for example, Nos. 3,415,644, 3,415,645,3,415,646, and 3,460,452. Generally, film units of this type include apair of rectangular support sheets, at least one of which istransparent, coated on their facing surfaces with a plurality of layersincluding a photo-sensitive imagerecording layer and an image-receptivelayer for supporting a visible transfer image. The two support sheetsare of equal width and are secured in face-to-face relation with thephotosensitive and image-receptive layers sandwiched therebetween, bybinding means including a binding sheet secured around and to the outersurfaces of the support sheets at their lateral margins and at one endmargin. The support sheets and the layers carried thereby also may belaminated to one another throughout the extent of their facing surfacesto form an integral unit. Attached to the other end of the supportsheets is a container of a liquid processing composition adapted to forma transfer image visible through the transparent support sheet whendistributed between the support sheets for permeation into thephotoexposed photo-sensitive, imagerecording layer. The binding sheetsand/ or binding strips are employed to form a seal between the containerand the support sheets for conducting the processing liquid from thecontainer between the support sheets in response to the application ofcompressive pressure to the container.

Processing of such a film unit is accomplished by advancing the filmunit, container foremost, between a pair of pressure applying memberswhich dispense the processing liquid from the container and distributeit between the sheets toward the opposite or trailing ends thereof. Thesheets of the film unit are retained in superposed relation followingcompetion of processing and image formation so that the image formedbetween the sheets is protectively enclosed and is viewed through thetransparent sheet. Among the advantages of this structure over the priorart is that the only processing step is distribution of the processingliquid within the film unit, and there is no necessity for subsequentprocessing and handling steps such as separation of the sheets nor arethere any waste materials to be disposed of because all components ofthe film units remain together as a unit prior to, during and subsequentto processing.

In the preferred embodiment of such a film unit disclosed and claimed,for example, in the copending and commonly assigned U.S. patentapplication of Edwin H. Land et al., Ser. No. 5,799, filed Jan. 26, 1970now U.S. Pat. No. 3,619,192, the transparent sheet is longer than theother sheet and the rupturable container of processing liquid is mountedon an extended end section of the transparent sheet adjacent an edge ofthe other sheet. To provide a more aesthetically pleasing product, i.e.a positive photographic print, as well as to aid in the distribution ofthe processing liquid, the binding means include an external bindingsheet which is generally rectangular and has a rectangular exposure andviewing opening therein. This binding sheet is secured in coveringrelation to the entire outer surface of the transparent sheet, except ofcourse in the region of the exposure and viewing opening, and themargins of the binding sheet are folded around at least the lateraledges and one (trailing) end edge of the support sheets and secured tothe margins of the other support sheet. In this way the binding sheetperforms a multiplicity of functions including retaining the supportsheets in face-to-face relation; providing an attractive border or framesurrounding the image; assisting in the distribution of the processingliquid by controlling the spacing between the pressure-applying memberswhich distribute the processing liquid; preventing admission of airbetween the sheets, at least at their lateral margins; and providingmeans for trapping and retaining excess processing liquid. Thisconstruction represents a substantial advance over prior art,self-developing film units particularly insofar as it results in agreatly improved and more pleasing product that is less expensive toproduce and easier to utilize.

As previously noted, the binding sheet performs a number of functions asa part of the film structure includmg:

(1) Providing an attractive, well-defined border around the completedimage which comprises the photographic print;

(2) Retaining the sheets together at their margins;

(3) Preventing admission of air between the sheets which might otherwiseinterfere with distribution of the processing liquid and/or becomeentrained in the liquid causing voids;

(4) Providing space for trapping and retaining excess processing liquidoverrun; and

(5) Aiding in the distribution of a viscous processing liquid as auniformly thin layer between the sheets to insure the proper amount ofliquid in all areas within the exposure opening in the binding sheet by:

(a) Spacing apart the pressure-applying members; and

(b) Permitting spreading of the liquid outwardly beyond the edges of theexposure aperture in regions underlying the binding sheets.

As is noted in the copending and commonly assigned U.S. patentapplication of Bachelder et al., Serial No. 744,912, filed July 15,1968, the binding sheet performs still another important function in thefilm manufacturing and assembly process. According to this application,the binding sheet is supplied as an elongated web which functions as acarrier on which other components of the film unit are mounted andattached during the assembly process as the web moves through theassembly apparatus.

Because the functions performed by the binding sheet are important andoften critical to assembly, processing and the appearance of theproduct, the physical specifications for this sheet are equallyimportant and critical necessitating the use of a relatively expensivematerial representing a substantial fraction of the overall cost of eachfilm unit. However, it will also be apparent that a major portion ofthis cost, e.g. 80%, represents waste, namely the material cut out ofthe binding sheet to form the relatively large exposure opening therein.

SUMMARY OF THE INVENTION Objectives of the present invention include theprovision of a novel and improved self-developing film of the generaltype described comprising structure for performing all of the functionsof the binder s'heet while eliminating the binder sheet itself. Thisfilm unit will function in essentially the same manner and can beprocessed by the same apparatus to produce a more pleasing product(photographic print) while offering a number of cost-saving advantagesin manufacture and assembly.

The objective of cost saving is achieved not only by eliminating thebinding sheet and employing less expensive means for securing the sheetsto one another, but by utilizing improvements in manufacturing andassembly techniques made possible by the novel structure and byproviding a structure in Which one of the sheets is narrower as well asshorter than the other sheet. Heretofore, both support sheets and thelayers carried thereon have been of unequal length and of equal width.However, in the preferred embodiment of the invention, the shorter sheetincludes the photosensitive image-recording layer which, in the case ofa film unit designed to produce color images such as described in theaforementioned patents, comprises a multiplicity of strata includingdifferently sensitized silver halide strata and associated dye developerstrata. Thus, the shorter sheet constitutes a relatively complex andexpensive structure and its cost per unit area is large relative to thecost of the longer sheet so that the shorter sheet represents a largeproportion of the total cost of each film unit. Accordingly, asubstantial cost saving can be realized by further reducing the area ofthe more expensive sheet to a minimum, specifically, by making it asnarrow as possible in addition to making it as short as possible. In thenovel and improved structure of the invention, the sheet which costs themost per unit area is both narrower and shorter than the less expensivesheet which, in this case, is the transparent sheet. Alternatively, thetransparent sheet may serve merely to aid in the distribution of theprocessing liquid in contact with another sheet carrying all of thelayers involved in the image-forming process.

For practical as well as aesthetic reasons, photographic transfer printsare usually surrounded by an image-free border having sharply definedinner edges. This border is uniformly wide and in the case of prior artfilm units of the type described, is provided by marginal portions ofthe binding sheet; paper, polymers, or composites thereof being suitablefor this purpose. The binding sheet providing the border is attached tothe exterior of the transparent support sheet through which the image isviewed and accordingly, is subjected to physical damage as Well asbecoming marred or discolored. Another function of the border providedby the binding sheet is to mask any image formed between the sheetsoutside of the area in which the image-forming exposure is made.

The present invention contemplates an improvement over this structure inthat the material which forms the combined mask and border is locatedwithin the film unit between the sheets so that the forward surface ofthe photographic print is a plain, smooth surface without attachments ordiscontinuities and the image is surrounded by a plain border whichcannot be physically damaged or discolored. The improved structure forsecuring the sheets to one another at their margins makes this possibleand the border or mask is formed as a layer on the inner surface of thetransparent sheet so that there is no waste material as in the casewhere an exposure aperture is formed in a sheet by cutting out arelatively large section thereof.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the product possessing the features,properties and the relation of components which are exemplified in thefollowing detailed disclosure, and the scope of the application of whichwill be indicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing wherein:

FIG. 1 is a perspective view, partially in section, illus trating aphotographic film unit embodying the invention;

FIG. 2 is a fragmentary, sectional view taken along the line 22 of FIG.1; and

FIG. 3 is a perspective view showing the film unit partially in section,illustrating the processing of the film unit.

DESCRIPTION OF PREFERRED EMBODIMENT The present invention is primarilyconcerned with the physical aspects or structure of a photographic,self-developing film unit adapted to incorporate a variety of diffusiontransfer systems for producing visible images. This film unit isparticularly adapted for incorporating diffusion transfer systemscapable of forming full color images which rely for color imageformation upon a differential in mobility or solubility of a dyeimage-providing material achieved as a function of development of aphotosensitive, image-recording material such as silver halide, so as toprovide an imagewise distribution of the dye image-providing materialwhich is diffusible and is selectively transferred, at least in part, bydiffusion to a superposed dyeable, image-receptive stratum to impartthereto, the desired transfer image.

The basic components of a multicolor image-forming system of this typeinclude a photosensitive layer comprising a plurality of selectivelysensitized silver halide strata each having associated therewith a dyeimage-providing material exhibiting desired spectral absorptioncharacteristics. Most commonly employed photosensitive layers of thistype are the so-called tripack structures employing blue-, greenandred-sensitive silver halide emulsions having associated therewith,respectively, yellow, magenta and cyan dye image-providing materials.For a more detailed disclosure of a system of this type for formingcolor images by diffusion transfer, reference may be had to a number ofU.S. patents including Pat. No. 2,983,- 606. Examples of specific dyeimage-providing materials of both the initially soluble or ditfusibletype and the initially non-diffusible type and their uses in colortransfer systems are to be found in U.S. Pats. Nos. 2,647,049;2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668;

2.983,606; 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552;3,227,554; 3,243,294; and 3,445,228.

Another essential component of the color image-forming system is apositive or image-receptive layer which is either initially superposedwith the photosensitive layer or is adapted to be brought intosuperposition with the photosensitive layer after photoexposure andduring processing. Generally, the image-receptive layer may comprise anyof the dyeable materials heretofore known in the photographic art forsupporting color transfer images including dyeable polymers such asgelatin, polyvinyl alcohol or gelatin containing a dye mordant. Suchlayers are designed to receive the imagewise distribution of diffused,dye image-providing material and are described in detail in many of theabove-mentioned patents including 3,227,550.

The image-forming system will also contain additional layers or stratafor performing a variety of functions including arresting or restrainingdevelopment, particularly in the dyeable stratum or in an associatedlayer, and especially in integral or composite structures in which thelayers including the photosensitive and image-receptive layers areretained together as a unit without separation. The film unit containsmeans for providing a reflecting layer between the photosensitive layerand the dyeable image-receptive layer so as to effectively mask thephotosensitive layer and provide a background for viewing, by reflectedlight, the dye image formed on the overlying dyeable stratum. Such meansfor providing a reflecting layer between the overlying photosensitiveand image-receptive layers may take a number of different forms. Forexample, a suitable reflecting agent may be incorporated in a liquidprocessing composition adapted to be distributed in a layer between thephotosensitive and image-receptive layers to effectuate the imagedifl'usion processing resulting in the positive image. Alternatively,the reflecting agent may be incorporated in a layer initally locatedbetween the photosensitive and image-receptive layers prior to exposureof the former or the reflective material which provides a background forthe transfer image may be formed in situ during the image-formingprocessing.

Another component of the dye image-forming system incorporated in thefilm unit structure of the invention is a liquid processing compositionadapted, when distributed within the film unit for permeation into theexposed photosensitive layer, to initiate and effectuate the diffusiontransfer process resulting in the formation of a dye image in theimage-receptive layer viewable by reflective light against a backgroundformed between the image-receptive layer and the photosensitive layer.This processing liquid is usually aqueous, alkaline, and contains aviscosity adding agent such hydroxyethyl cellulose, to aid in thespreading of the liquid in a thin layer within the film unit. It mayalso contain a reflecting agent such as titanium dioxide. For examplesof specific materials and compositions, reference may be made to many ofthe aforementioned patcuts, or U.S. Pats. Nos. 3,415,644; 3,415,645;3,415,646; and 3,473,925.

The various layers constituting the image-forming diffusion transfersystem are supported on and sandwiched between a pair of dimensionallystable and preferably liquid impermeable support layers or sheets. Eachsheet and the layers coated thereon during the manufacturing of the filmunit may be in the form of separate, individual elements which arelaminated to one another by and during distribution of the processingliquid between the elements. In the alternative, the two elementscomprising the support sheets and layers coated thereon may be laminatedto one another prior to photoexposure to form an integral structure, inwhich case, the processing liquid is distributed between the layers ofthe integral structure simultaneously delaminating and laminating theselayers to one another to form another integral structure containing anadditional layer constituted by the processing liquid.

Reference is now made to the drawing wherein there is illustrated aself-developing photographic film unit embodying the invention. Thebasic components of the film unit include a first rectangular,sheet-like element designated 10 and a second rectangular, sheet-likeelement designated 12. Each of these elements comprises a dimensionallystable support sheet coated thereon with some or all of the variouslayers and strata previously described and/or conventionallyincorporated in photographic film units of this type. In the preferredembodiment shown and described, the first element 10 is preferablyopaque to actinic light and includes a support sheet which, during themanufacturing process, is coated at least on one side with thephotosensitive layer, generally designated 11 in FIG. 2, including thevarious photosensitive strata and associated dye image-formingmaterials. It also may be coated during the manufacturing process withauxiliary layers and strata including the image-receptive layer, a layerfor arresting or inhibiting the development process and/or a reflectivelayer for providing a background for the dye image supported by theimage-receptive layer. The layer (or strata) coated on the support sheetcomprising second element 12 is generally designated 13 in FIG. 2.

In accordance with the invention, the first element is substantiallysmaller than the second element and, in order to realize the largestpossible cost-saving, it should support as many of the various layers asis possible, consistent with the constraints imposed thereon by themanufacturing process, in order that the first element will have ahigher cost per unit area than the larger second element. It should berealized, of course, that where additional expense may be incurred byincorporating a particular layer or stratum as a part of the firstelement will be 'more expensive than coating the same layer or stratumon the second element and such expense will outweigh any possiblesavings in material, then such a layer or stratum should be incorporatedas part of the second element as layer 13. All of those factors whichdictate which particular layer will be initially incorporated as a partof element 10 or 12, should be apparent to anyone skilled in the art,bearing in mind the cost-saving objective which is achieved by utilizinga minimum area of a relatively expensive sheet material and a relativelylarger area of a less costly sheet material.

Each of sheet-like elements 10 and 12 comprises a dimensionally stablesupport sheet and the elements are secured to one another inface-to-face relation with the layers (11 and 13, respectively) coatedthereon and comprising components of the dye image transfer system,e.g., the photosensitive and image-receptive layers, sandwiched betweenthe support sheets. The layers 11 and 13 coated on the support sheets ofelements 10 and 12 are designed to perform functions involved in theexposure and/or processing of the film unit to form a finished andattractive photographic print. In addition to the layers sandwichedbetween the supports, other layers may be coated on the outside of thesupports for performing functions such as, for example, altering theoptical properties of these supports, preventing abrasion,opacification, and the like. The support for element 10 is preferablyopaque to actinic light to permit processing of the film unit in thelight (as will be described hereinafter) as Well as to permit aplurality of the film units to be arranged in stacked relation in a filmcontainer or cassette and exposure of the film unit at one end of thestack without exposure of underlying film units. The support sheet forsecond element 12 is preferably transparent to permit photoexposure ofthe photosensitive layer sandwiched between the support sheets and topermit viewing of the positive transfer image when image formation iscompleted. As examples of materials useful for the support sheets,mention may be made of polymeric films derived from ethylene glycolterephthalic acid, vinyl chloride polymers, polyvinyl acetate, cellulosederivatives, and the like.

Element 12 is substantially longer and wider than element and includes aleading end section 14 extending beyond the leading edge 16 of firstelement 10; a trailing end section 18 extending beyond the trailing edge20 of element 10 and lateral marginal sections 22 extending beyond thelateral edges 24 of element 10. The two sheets are preferably arrangedwith respect to one another so that the lateral marginal sections 22 areof equal width while the leading end section 14 is substantially longerthan trailing end section 18.

The two elements are secured together at their lateral edges by a pairof binding strips 26, each secured to the lateral margin of the outersurface of element 10 and to the adjacent lateral marginal section 22 ofsheet 12. Materials useful for the binding strips include paper,polymeric films or laminates composed of different ma terials includingpaper and polymers.

The processing liquid for each film unit is supplied in a rupturablecontainer 28 of a type well-known in the art and described, for example,in US. Pat. No. 2,543,181. Container 28 is formed by folding arectangular blank of a fluid and vapor impervious sheet materialmedially and sealing the marginal sections of the blank to one anotherto form a cavity for containing processing liquid designated 30. Theseal between the longitudinal marginal sections 32 is weaker than theseals at the ends of the container so that in response to theapplication of compressive pressure to the walls of the container in theregion of the liquid-filled cavity, there will be generated within theliquid hydraulic pressure sulficient to separate longitudinal marginalsections 32 throughout the major portion of their length to form adischarge mouth which is preferably equal in length to the liquid-filledcavity. The latter is preferably at least substantially equal in lengthto the width of the exposed area of the photosensitive layer. Container28 is mounted on leading end section 14 of element 12 with the edge ofmarginal sections 32 located closely adjacent the leading edge 16 ofelement 10, and the opposite longitudinal edge of the container at whichthe blank is folded, is located closely adjacent and in parallelrelation with the end edge of element 12.

Means are provided for securing container 28 to elements 12 and 14 so asto retain the container in place and provide a passage for conductingthe liquid contents of the container from the cavity within thecontainer between layers of elements 10 and 12 as compressive pressureis applied to the container to eject its liquid contents therefrom.

These last-mentioned means include an elongated retaining strip 34folded longitudinally to form two sections, one of which is adhered toelement 10 adjacent the leading edge thereof between element 10 and alongitudinal edge portion of container 28. The other section ofretaining strip 34 is folded around the longitudinal edge portion of thecontainer and is secured to the outer marginal surface of the container.The overall length of the container is approximately equal to the widthof element 10 and retaining means in the form of relatively shortretaining strips 36 are secured to the end margins of container 28 andlateral marginal sections 22 of element 12. Retaining strips 36 arepreferably equal in length to the width of the container and equal inwidth to retaining strips 26 so that one end edge of each retainingstrip 36 abuts an end edge of one of the retaining strips 26 while theother end edge of each retaining strip 36 is aligned substantially withthe leading edge of second element 12. Means in the form of anotherretaining strip 38, approximately equal in length to the width ofelement 12, is secured to one marginal section 32 of continer 28 and theouter surface of the leading edge section of element 10 so as to bridgethe gap between the container and element 10 and provide a passage forconfining the processing liquid within the film unit as the liquid isejected from the container. Retaining strips 34, 36 and 38 may be formedof the same material as binding strips 26 and are adhered to theelements and the container in the same manner.

In the embodiment of the film unit in which first and second elements 10and 12 are separate, individual elements secured together only at theirmargins, the liquid contents of container 28 will be spread between theelements as the film unit is moved, container foremost, between a pairof juxtaposed members which first apply compressive pressure to thecontainer to rupture the seal between marginal sections 32, ejecting theliquid from the container between the marginal sections so that it isforced to flow between elements 10 and 12. In the alternative embodimentof the film unit in which elements 10 and 12 are laminated to oneanother to form an integral unit, the bond between a particular pair ofadjacent layers or strata will be weaker than the physical bond betweenany other pair of adjacent layers or strata so that the hydraulicpressure of the liquid which is confined within the film unit, willrupture the laminate where the bond is weakest, permitting the liquid tospread between elements 10 and 12 toward the trailing end of the filmunit.

Another function of lateral binding strips 26 is illustrated in FIG. 3in which there is shown a typical pair of pressure-applying members inthe form of rollers 40 and 42 mounted in juxtaposition for rotationabout axes located in a common plane. Processing means including rollersare well-known in the art and the rollers are biased toward one anotherto apply compressive pressure to the film unit, progressing from theleading end toward the trailing end so as first to eject the liquidcontents of the container and then distribute the liquid betweenelements 10 and 12 toward the trailing ends of the elements. Lateralbinding strips 26 provide means for predeterminately spacing apart thepressure-applying rollers so as to provide a space between the medialportions of elements 10 and 12 in which the processing liquid can bespread in a layer of predetermined thickness. It will be apparent fromFIG. 3 that the greatest cross-sectional thickness of a transversesection of a film unit in the region in which the photosensitive layeris exposed, occurs near the margins of the film unit where the lateralbinding strips 26 are adhered to the outer surface of element 10. Thisthickness includes a binding strip, elements 10 and 12, and anyadditional layers or strata coated on the elements in this region. Theaggregate cross-sectional thickness of the portion of the film unitintermediate binding strips 26 will be less so that during spreading ofthe processing liquid, the medial portions of elements 10 and 12 will beforced apart into engagement with rollers 40 and 42 providing a spacebetween the elements in which the processing liquid is spread. The depthof this space is a function of the thickness of the binding strips.

Other functions performed by the binding strips are to prevent escape ofthe processing liquid from between the elements 10 and 12 at the marginsthereof and prevent admission of air between the elements. Preventingescape of processing liquid at the margins of the film unit is obviouslyimportant, not only because such liquid may contaminate the processingapparatus, but the loss of liquid may mean that there will beinsuflicient liquid to complete image formation throughout the exposedarea of the photosensitive layer. The exclusion of air from betweenelements 10 and 12 is important because such air tends to interfere withthe spreading of the liquid since it must be advanced ahead of theadvancing mass of liquid and/or may become entrained in the liquid toform voids in the layer of liquid which appear as defects in the visibleimage.

The first and second elements 10 and 12 are secured to one another attheir trailing ends by retaining means in the form of a trailing endretaining strip 44, equal in length to the width of element 12 andsecured along one edge to trailing end section 18 of second element 12adjacent the trailing edge of the second element. End retaining strip 44is folded upon itself and secured along its opposite longitudinal marginto the outer surface of first element adjacent the trailing edge thereofand the trailing end portions of lateral binding strips 26. The ends ofretaining strip 44 are adhered to the lateral margins of the trailingend section of element 12.

In order to insure the spreading of the processing liquid in a layer ofpredetermined uniform thickness throughout an area at least coextensivewith the exposed area of the photosensitive layer, excess processingliquid is supplied within the container. Means are provided within thefilm unit for trapping and retaining any excess processing liquid thatmay be spread beyond the trailing edge of first element 12. In the formshown, these liquid trapping and retaining means comprise a pocketformed by retaining strip 44 and a spacing element (or elements) 46enclosed within the pocket by retaining strip 44 and the trailing endsection 18 of element 12. Spacing element 46 is designed to space apartthe inner surfaces of retaining strip 44 and second element 12 as thepressure-applying members, e.g., rollers 40 and 42, pass over thetrailing end of the film unit so that a space remains within the filmunit in which the excess processing liquid overrun is trapped andretained. Spacing elements suitable for this purpose are well-known inthe art and in the form shown, spacing element 46 consists of a stripformed with openings in which the excess processing liquid can collect.Other forms of spacing elements find equal utility in the film unit ofthe invention and these include a spacing element of the type shown anddescribed in the copending and commonly assigned US. patent applicationof Richard J. Chen, Ser. No. 726,252 now abandoned, filed May 2, 19 68.

Provision is also made for releasing air from the liquid trapping andretaining space provided by spacing element 46 and retaining strip 44.This may be accomplished in a number of different ways such as byproviding slits or perforations in retaining strip 44, or providingregions in which the retaining strip is not adhered to either the secondelement 12 adjacent the lateral edges thereof or to the first element 10adjacent the trailing edge thereof, as suggested in the aforementionedChen application.

As previously noted, the film unit includes a masking layer designated50 designed to perform a number of functions and having as its basicfunction, the provision of a sharply defined image-free bordersurrounding a high quality transfer image extending to the edges of theborder. Masking layer 50 is applied to the second element duringmanufacture, extends to the edges of the second element and is formedwith a rectangular opening 52 having sharply defined edges. Opening 52defines the extent of the visible image, is slightly smaller than firstelement 10 and is symmetrically located with respect to the firstelement with the edges of opening 52 parallel with and equally spacedfrom adjacent edges of the second element. The edges of the opening 52are also spaced inwardly from the edges of the film unit so as to belocated inwardly from the edges (inner) of binding strips 26 andretaining strips 38 and 44, such that when viewed from the side of thetransparent element, the edges of the strips underlie the masking layer.The binding and retaining strips limit and define the region in whichthe liquid is distributed. This construction in which the edges of thestrips underlie the masking layer and are outside the image area issignificant because it permits the processing liquid to be distributedlaterally and lengthwise beyond the edges of the image area into regionsunderlying the masking layer. This is important because it has beenfound that the various layers near and particularly outside of the edgesof the region in which the liquid is distributed, will absorb theprocessing liquid so that within this region at the edges thereof, theremay be insufiicient processing liquid to insure proper and completetransfer image formation. However if, as in the construction of theinvention, the

10 liquid is distributed outwardly beyond the edges of the region inwhich the visible portion of the transfer image is formed, that is,behind the masking layer, then the image will appear to be of uniformhigh quality at its edges defined by the edges of the opening in themasking layer.

Masking layer 50 may be of any desired color although white is, bycustom and usage, the more preferred color; and comprises a pigment suchas titanium dioxide carried in a suitable binder, preferably a polymerwhich is a liquid during formation of the masking layer and solidifiesto form a stable adherent layer. The masking layer can be formed orapplied to element 12 by a number of wellknown systems including, forexample, conventional printing methods such as the gravure process. Themasking layer is located layerwise within the film unit such that theprocessing liquid will be distributed behind the masking layer, that is,to the side thereof opposite the transparent support. This is to insurethat any diffusible, image-providing material (dye) formed outside(laterally and lengthwise) of the image area defined by opening 52, willunderlie the masking layer and will be hidden from view thereby. Thepreferred location of the masking layer is betweeen the image-receptivelayer 13 and the layers or strata associated therewith as shown in FIG.2 and may be located directly on the inner surface of support sheet 22.However, depending on the nature and composition of the masking layerand particularly, the composition of the polymeric binder and thedensity of the reflecting agent, the masking layer may be disposedwithin the multilayer structure, for example, between the photosensitivelayer designated 11 and the image-receptive layer.

In the preferred embodiment of the invention, the polymeric binder ofthe masking layer is insoluble in the aqueous alkaline processingliquid, is preferably hydrophobic and at most, very slightly permeableto water. The masking layer should be as thin as possible consistentwith providing the requisite opacity and reflectance, a function of thedensity and distribution of the reflecting agent, preferably titaniumdioxide. So-called acrylic latex base paints and similar compounds areconsidered especially suitable for forming a masking layer having therequired characteristics mentioned above. An example of such a compoundis given as follows:

Grams Water 17.0

' Tamol731 11.0 Antifoamer (e.g., tributyl phosphate) 2.0 Ethyleneglycol 22.0 Preservative (sodium pentachlorophenate) 0.5 2% hydroxyethylcellulose 84.0

Rutile titanium dioxide 400.0

Tr-ade name of sodium salt of polymeric carboxylic acid, sold by Rohm &Haas.

The above is ground at high speed and mixed with the following:

Grams Polymer binder 600.0 Tributyl phosphate 2 5.0 Antifoamer 2 2.0

Ammonium hydroxide 28%.

1 Such as a 46% acrylic emulsion polymer sold by Rollin 8.: Haas underthe trade name Rhoplex MV-l.

2 Premixed.

The effectiveness of masking layer 50 in covering or masking anytransfer image formed therebehind is a function of two factors, namely,the permeability of the layer by the dye solvent, e.g., water, and thecontent or concentration of titanium dioxide. A masking layer having therequisite covering power and reflectance can be formed by coating theabove composition on second element 12 to provide a minimum titaniumdioxide concentration of the order of 600.0 milligrams per square foot.However, lower titanium dioxide concentration may provide covering poweracceptable for any application depending upon the distribution oftitanium dioxide and the location of other layers or strata with respectto the masking layer. Of course, higher concentration of titaniumdioxide up to a maximum of about 2,500 milligrams per square foot willprovide a whiter, higher reflectance border more capable of masking anyimage formed therebehind.

Masking layer 50 is illustrated in FIG. 2 as being coated betweenimage-receptive layer 11 and support sheet 22. This location ispreferred for a number of reasons including the fact that the variousstrata which make up the film unit include an acid-containing orneutralizing layer for reducing the pH to arrest the development processas disclosed, for example, in the copending US. patent application of E.H. Land, Ser. No. 782,056, filed Dec. 9, 1968, now US. 'Pat. 3,573,043.This neutralizing layer generally has associated therewith a spacer ortiming layer for delaying the neutralizing reaction and both of theselayers are located between the image-receiving layer and the maskinglayer providing a barrier which aids in preventing permeation of themasking layer by imageforming dyes.

As noted in many of the aforementioned patents and applications, amasking layer including a reflecting pigment is formed between thephotosensitive and imagereceptive layers throughout the areas thereof inwhich an image is formed, to provide a reflective background for thetransfer image formed in the image-receptive layer and to mask or coverthe photosensitive layer and the image formed therewith. This maskingand reflecting layer may be formed in a number of ways. For example, asnoted in the copending U.S. patent application of Edwin H. Land, Ser.No. 43,782, filed June 5, 1970, an inorganic reflecting pigment such astitanium dioxide is dispersed in the processing liquid which is spreadin a layer between the photosensitive layer and the image-receptivelayer to provide a layer exhibiting the requisite optical transmissionand reflection densities. Obviously, this second masking layer willextend from edge-to-edge of the area in which the processing liquid isdistributed so that it will be located behind masking layer 50 where itwill contribute further to the masking of any image formed behindmasking layer 50..

In an alternative embodiment of the film unit, the masking andreflecting layer located betweenthe photosensitive and image-receptivelayers to provide a background for viewing the color transfer image maybe provided, in whole or in part, as a preformed layer of the film unitsuch as disclosed in the copending U.S. patent applications of Edwin H.Land, Ser. Nos. 846,441, filed July 31, 1965, now U.S. Pat. 3,615,421and 3,645, filed Jan. 19, 1970, now US. Pat. 3,620,724; or thereflecting pigment may be generated in situ as is disclosed in thecopending US. patent applications of Edwin H. Land, Ser. Nos. 43,741,now US. Pat. 3,647,434 and 43,742, now US. Pat. 3,647,435, both filedJune 5, 1970. In these latter embodiments, the masking and reflectinglayer will be located behind masking layer 50 so as to furthercontribute to the effectiveness thereof.

Masking layer 50 may be provided between the imagereceptive layer andthe photosensitive layer particularly when the binder for the pigment isa polymer that is insoluble in water and forms a layer which is at leastpoorly permeable and preferably impermeable to the solvent (i.e. Water),of the processing composition or, as disclosed, is essentiallyhydrophobic. Such a masking layer 50 provides an effective barrier tothe diffusion of the imageforming dyes while the masking and reflectinglayer formed between the photosensitive and image-receptive layers andhence between the photosensitive layer and the masking layer 50, willalso contribute to the effectiveness of the latter. While in thepreferred embodiment the masking layer 50 is described as including apolymeric binder which is water insoluble and preferably hypro phobic sothat the masking layer is impermeable or at least poorly permeable, themasking layer may also be formed employing a binder which is soluble inwater and hence more permeable to the dilfusible image-forming dyes.Suitable polymeric binders of this type useful in masking layer 50include, for example, gelatin and polyvinyl alcohol. Such layers provevery eflective, particularly when located between the image-receptivelayer and support layer 22 although such a masking layer may be locatedbetween the image-receptive layer and the photosensitive layer with themasking and reflecting layer which is formed therebetween, furthercontributing to the elfectiveness of masking layer 50 It will beappreciated from the foregoing that the novel film unit structure, inachieving the objects of the invention, represents a substantial advancein the art particularly insofar as it constitutes a construction havingfewer and more easily formed and assembled components, and utilizes lessmaterial while minimizing waste materials. To these advantages are addedthe achievement of a more esthetically pleasing product, i.e. aphotographic print, which is less subject to damage.

Since certain changes may be made in the above product without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

What is claimed is:

1. In a photographic film unit adapted to be exposed to form an imageand comprising first and second rectangular supports secured inface-to-face relation, a lightsensitive, image-recording layer and animage-receptive layer between said supports, at least said secondsupport being substantially transparent to permit viewing of an imageformed between said supports, and a rupturable container of liquidprocessing composition for forming a visible image in saidimage-receptive layer when distributed between said supports forpermeation into said image-recording layer, the improvement comprising,in combination said second support being larger than said first supportand said supports being arranged with margins of said second supportextending beyond the edges of said first support;

first retaining means secured to the marginal surfaces of said supportsfacing in the same direction along these edges of said supports toretain the latter in face-to-face relation prior to, during andsubsequent to exposure and processing;

second retaining means securing said rupturable container to saidsupports adjacent the fourth edge of said first support for conductingthe liquid contents of said container between said supports in responseto the application of compressive pressure to said container; and

a masking layer carried on said second support and located between thelatter and said image-recording layer, said masking layer extending tothe edges of said second support and having a rectangular medial openingwith length and width dimensions smaller than the length and width ofsaid first support and located with the edges of said first supportunderlying said masking layer.

2. A photographic film unit as defined in claim 1 wherein said firstretaining means include an end and two lateral retaining strips securedto the outer surface of said first support and the inwardly facingsurface of said second support at one end and two lateral, marginalportions thereof.

3. A photographic film unit as defined in claim 2 wherein the inneredges of said end and lateral retaining strips furthest from the outeredges of said second support underlie said masking layer.

4. A photographic film unit as defined in claim 2 wherein said containeris rectangular and is mounted on the other end portion of said secondsupport, and said other end portion extending beyond an end edge of said13 first support has a length at least equal to the shorter dimension ofsaid container.

5. A photographic film unit as defined in claim 4 wherein said secondretaining means include a fourth retaining strip secured to a margin ofsaid container and to the outer surface of said first support at theother end margin thereof.

6. A photographic film unit as defined in claim 5 wherein the edge ofthe portion of said fourth retaining strip secured to said first supportunderlies said masking layer.

7. A photographic film unit as defined in claim 5 wherein said containeris secured to said other end marginal portion of said second support atleast along three margins of said container.

8. A photographic film unit as defined in claim 7 wherein said secondretaining means further include a fifth retaining strip secured to thesurface of said second support underlying said container, folded aroundand secured to the outer surface of the margin of said containerfurthest from said fourth retaining strip.

9. A photographic film unit as defined in claim 2 further includingliquid trapping and retaining means secured between said second supportand said end retaining strip.

10. A photographic film unit as defined in claim 1 wherein said maskinglayer is located between said imagereceptive layer and said secondsupport and includes a light-reflecting agent for efiectively maskingsaid imagerecording layer and any image formed in said image-receptivelayer underlying said masking layer.

11. A photographic film unit as defined in claim 1 wherein said maskinglayer includes a light-reflecting agent suspended in a polymeric binderfor effectively masking said image-recording layer.

12. A photographic film unit as defined in claim 11 wherein saidsupports and said layers are bonded together as an integral unit.

13. A photographic film unit as defined in claim 11 wherein saidimage-recording layer includes at least a light-sensitive silver halidestratum and an associated dye image-providing material and saidimage-receptive layer includes a dyeable stratum.

14. A photographic film unit as defined in claim 13 wherein said binderis at least poorly soluble in said liquid processing composition.

15. A photographic film unit as defined in claim 13 wherein said binderis substantially insoluble in said processing liquid.

16. A photographic film unit as defined in claim 14 wherein said maskinglayer is located between said imagerecording layer and saidimage-receptive layer.

17. A photographic film unit as defined in claim 14 wherein said maskinglayer is located between said imagereceptive layer and said secondsupport.

18. A photographic film unit as defined in claim 13 wherein said liquidprocessing composition includes water and said binder is poorly solublein water.

19. A photographic film unit as defined in claim 1 wherein said supportsand said layers are bonded together as an integral unit.

20. In a self-developing photographic film unit including a pair ofexternal support sheets, at least one of which is transparent, securedin face-to-face relation, an image-recording layer including at least alight-sensitive silver halide stratum and an associated dyeimageproviding material and an image-receiving layer including a dyeablestratum, located between said support sheets, and a rupturable containercoupled with said support sheets and containing a liquid processingcomposition including a solvent for said dye image-providing material,adapted to be distributed between said support sheets for permeationinto said image-recording layer to render said dye image-providingmaterial transferable by diffusion to said dyeable stratum, theimprovement comprising:

a masking layer between said one support sheet and at least saidimage-recording layer extending to the edges of said one support sheetand having a medial opening smaller than said image-recording layer;

said masking layer including a light reflecting agent suspended in apolymeric binder at least poorly soluble in said liquid processingcomposition for effectively masking from view, portions of said imagerecording layer and any of said dye image-forming material rendereddifiusible to said image-receptive layer and underlying said maskinglayer..

21. A photographic film unit as defined in claim 20 wherein said supportsheets and said layers are bonded together as an integral unit.

22. A photographic film unit as defined in claim 20 wherein said maskinglayer is located between said imagerecording layer and saidimage-receptive layer.

23. A photographic film unit as defined in claim 22 wherein said binderis insoluble in said liquid processing composition.

24. A photographic film unit as defined in claim 20 wherein saidimage-receptive layer is located between said image-recording layer andsaid one support sheet and said masking layer is located between saidimage-recording layer and said image-receptive layer.

25. A photographic film unit as defined in claim 20 wherein saidimage-receptive layer is located between said image-recording layer andsaid one support sheet and said masking layer is located between saidimage-receptive layer and said one support sheet.

26. A photographic film unit as defined in claim 20 wherein said liquidprocessing composition includes water and said binder is poorlypermeable to Water.

27. A photographic film unit as defined in claim 26 wherein said binderis hydrophobic.

References Cited UNITED STATES PATENTS 3,161,516 12/1964 Hamilton et a1.96-29 3,256,090 6/1966 Booth 96-29 3,320,065 5/1967 Campbell 96-29NORMAN G. TORCHIN, Primary Examiner I. L. GOODROW, Assistant ExaminerU.S. Cl. X.R. 96-76 R

